Make more code work with no_std. (#407)

* Make more code work with no_std.

no_std support is still incomplete, but this patch takes care of the
bulk of the straightforward parts.

wasmtime-environ/src/cache/config.rs

@@ -1,6 +1,9 @@
 //! Module for configuring the cache system.
 
 use super::worker;
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
+use core::time::Duration;
 use directories::ProjectDirs;
 use lazy_static::lazy_static;
 use log::{debug, error, trace, warn};
@@ -13,10 +16,7 @@ use std::fmt::Debug;
 use std::fs;
 use std::mem;
 use std::path::{Path, PathBuf};
-use std::string::{String, ToString};
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::time::Duration;
-use std::vec::Vec;
 
 // wrapped, so we have named section in config,
 // also, for possible future compatibility

wasmtime-environ/src/cache/config/tests.rs

@@ -1,7 +1,7 @@
 use super::CacheConfig;
+use core::time::Duration;
 use std::fs;
 use std::path::PathBuf;
-use std::time::Duration;
 use tempfile::{self, TempDir};
 
 // note: config loading during validation creates cache directory to canonicalize its path,

wasmtime-environ/src/cache/tests.rs

@@ -3,17 +3,17 @@ use super::*;
 use crate::address_map::{FunctionAddressMap, InstructionAddressMap};
 use crate::compilation::{CodeAndJTOffsets, Relocation, RelocationTarget, TrapInformation};
 use crate::module::{MemoryPlan, MemoryStyle, Module};
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::cmp::min;
 use cranelift_codegen::{binemit, ir, isa, settings, ValueLocRange};
 use cranelift_entity::EntityRef;
 use cranelift_entity::{PrimaryMap, SecondaryMap};
 use cranelift_wasm::{DefinedFuncIndex, FuncIndex, Global, GlobalInit, Memory, SignatureIndex};
 use rand::rngs::SmallRng;
 use rand::{Rng, SeedableRng};
-use std::boxed::Box;
-use std::cmp::min;
 use std::fs;
 use std::str::FromStr;
-use std::vec::Vec;
 use target_lexicon::triple;
 
 // Since cache system is a global thing, each test needs to be run in seperate process.

wasmtime-environ/src/cache/worker.rs

@@ -6,10 +6,12 @@
 //! Background tasks can be CPU intensive, but the worker thread has low priority.
 
 use super::{cache_config, fs_write_atomic, CacheConfig};
+use alloc::vec::Vec;
+use core::cmp;
+use core::time::Duration;
 use log::{debug, info, trace, warn};
 use serde::{Deserialize, Serialize};
 use spin::Once;
-use std::cmp;
 use std::collections::HashMap;
 use std::ffi::OsStr;
 use std::fs;
@@ -19,10 +21,8 @@ use std::sync::mpsc::{sync_channel, Receiver, SyncSender};
 #[cfg(test)]
 use std::sync::{Arc, Condvar, Mutex};
 use std::thread;
-use std::time::Duration;
 #[cfg(not(test))]
 use std::time::SystemTime;
-use std::vec::Vec;
 #[cfg(test)]
 use tests::system_time_stub::SystemTimeStub as SystemTime;
 

wasmtime-environ/src/cache/worker/tests.rs

@@ -1,6 +1,6 @@
 use super::*;
 use crate::cache::config::tests::test_prolog;
-use std::iter::repeat;
+use core::iter::repeat;
 use std::process;
 // load_config! comes from crate::cache(::config::tests);